CN101400832A - Process for preparing catalyst material - Google Patents

Abstract

This invention aims to provide a catalyst material that densely supports an active substance, thereby exhibiting high catalytic performance and being well-suited for use as, for example, a fuel cell electrode. To achieve the above objective, this invention provides a method for preparing the catalyst material, comprising: an electrochemical polymerization step, i.e., electrochemically polymerizing a heterocyclic compound, thereby coating the surface of a conductive material with polycyclic coordination molecules derived from the heterocyclic compound; and a metallization step, i.e., chelating a catalytic metal onto the coating of the polycyclic coordination molecules, characterized in that the potential applied during the electrochemical polymerization is 0.8 to 1.5 V.

Description

Method for preparing catalyst material

technical field

The present invention relates to a method for preparing a catalyst material, and in particular, relates to preparing a catalyst material that densely supports active substances, thereby having high catalytic activity and being suitable for use as a fuel cell catalyst.

Background technique

Electrode systems, such as electrode catalysts, which have been modified with macrocyclic compounds such as porphyrins, chlorophylls, phthalocyanines, tetraazinazocenes or Schiff bases, or their derivatives have been studied more recently. And the electrochemical multi-electron reduction properties of molecular oxygen (O ₂ ) induced by the use of electrode catalysts are expected (see "Journal of the Japan Surface Technology Association", Hyomen Gijyutsu, Vol. 46, No. 4, 19-26, and "For Polymers for Advanced Technology", No. 12, pp. 266-270, 2001), these electrode systems, such as electrode catalysts replacing platinum (Pt) and its alloys, can be used in fuel cells (such as phosphoric acid fuel cells or polymer fuel cells battery) cathode (oxygen-hydrogen).

However, the catalytic activity of electrode systems utilizing any of the aforementioned macrocyclic compounds is insufficient to preclude their use in fuel cells. Under these conditions, there is a need to develop catalyst materials with high catalytic performance and applicability.

Contents of the invention

Accordingly, it is an object of the present invention to provide a catalyst material which densely supports active substances, thereby having high catalytic performance, and which can be preferably used as, for example, a fuel cell electrode.

In order to solve the above-mentioned problems, the inventors of the present invention first investigated the reason why an electrode catalyst using a macrocyclic compound does not have a sufficiently high catalytic activity. They deduced from their investigation that in macrocycles, when the active material is supported on a catalyst support, the density of the active material decreases, and thus the activity of the catalyst electrode using the macrocycle decreases. The inventors of the present invention have found through investigation that if the support is coated with a heteromonocyclic compound or a polycyclic polymer derived from a heteromonocyclic compound, many _MN4 structures in which the catalyst metal is chelated are formed, thereby obtaining a Catalyst material with high catalytic activity.

Accordingly, the inventors of the present invention have invented a catalyst material prepared by chelating a catalytic metal to the chelation sites of a polycyclic polymer-coated conductive material via the Polycyclic polymers are formed, characterized in that said polycyclic polymers are derived from heteromonocyclic compounds.

After meticulous research, the present inventors found that when polycyclic complex molecules are obtained by electrochemically polymerizing heteromonocyclic compounds under specific conditions (applied voltage, solvent, supporting electrolyte), the obtained catalyst material has a dense Active material, and having significantly improved catalytic activity, the present inventors thus achieved the present invention. Furthermore, the present inventors have found that when a specific polymerizable ligand is used as a polycyclic complex molecule for electrochemical polymerization, the resulting catalyst material has significantly improved catalytic activity, whereby the present inventors have achieved the present invention. And after studying the characteristics of the conductive material used as a carrier, the inventors also found that when the material has a specific specific surface area and an average particle size, the obtained catalyst material has a significantly improved catalytic activity, and the inventors thus achieved the invention. In addition, the inventors have also found that repeating electrochemical polymerization and/or chelation (metallization) of catalytic metals several times can effectively increase the density of the active material loaded on the catalyst material and improve the catalytic activity of the catalyst material, The present inventors thus achieved the present invention. In addition, the present inventors have also found that the use of auxiliary ligands when repeating electrochemical polymerization and/or chelation (metallization) of catalytic metals several times can effectively increase the possibility of chelation of catalytic metals. the invention. In addition, the present inventors have also found that when noble metals and transition metals are simultaneously chelated onto the coating, the resulting catalyst material has significantly improved catalytic activity, whereby the present inventors have achieved the present invention.

First, the present invention is a method for preparing a catalyst material, comprising: an electrochemical polymerization step, that is, electrochemically polymerizing a heteromonocyclic compound, so that the surface of the conductive material is derivatized from polycyclic coordination molecules of the heteromonocyclic compound coating; and the step of metallization, ie, the chelation of catalytic metals to the coating of said polycyclic polymer, characterized in that the potential applied during the electrochemical polymerization is between 0.8 and 1.5V.

In the present invention, preferred examples of heteromonocyclic compounds include those each having pyrrole, dimethylpyrrole, pyrrole-2-carboxyaldehyde, pyrrol-2-ol, vinylpyridine, aminobenzoic acid, aniline, or thiophene as a basic skeleton. monocyclic compounds. Preferable examples of polycyclic polymers obtained by electrochemical polymerization include polypyrrole complexes, polyvinylpyridine complexes, polyaniline complexes, and polythiophene complexes. Methods for electrochemically polymerizing heteromonocyclic compounds are known from various known documents.

In the present invention, preferably, the electrochemical polymerization step is performed in any of various known solvents, and particularly preferably in a water-methanol or water-ethanol mixed solvent.

In addition, preferably, the electrochemical polymerization step is performed using NH ₄ ClO ₄ or PTS as a supporting electrolyte.

In the method for producing a catalyst material of the present invention, any of various known electrochemically polymerizable heteromonocyclic compounds is used as the heteromonocyclic compound. In particular, when using 2-(1H-pyrrol-3-ylpyridine), which is a polymerizable ligand in which pyridine and pyrrole are linked together, catalyst materials with increased catalytic activity are obtained.

In the present invention, the conductive material as a carrier of the catalyst material preferably has a specific surface area of 500 to 2000 m ² /g, more preferably 800 to 1500 m ² /g. Furthermore, the conductive material preferably has an average particle size of 3 to 30 nm, more preferably 3 to 10 nm.

In the method for preparing a catalyst material according to the invention, said electrochemical polymerization and/or metallization step is preferably carried out more than once. In particular, the method of preparing the catalyst material comprises: an electrochemical polymerization step, i.e., electrochemically polymerizing a heteromonocyclic compound, so that the surface of the conductive material is coated with a polycyclic polymer derived from said heteromonocyclic compound; and The metallization step, ie the chelation of catalytic metals to the coating of said polycyclic polymer, is preferably carried out more than once in the process, said electrochemical polymerization step and/or metallization step. These steps make it possible to increase the density of the active species supported on the catalyst material, thereby increasing its catalytic activity.

In the present invention, preferably, at least two kinds of heteromonocyclic compounds are electrochemically polymerized in the electrochemical polymerization step.

In the present invention, preferably, not only noble metals but also transition metals are chelated in the metallization step.

Preferably, the method for preparing the catalyst material of the present invention further includes a heat treatment step performed after the metallization step. Heat treatment can significantly improve the catalytic activity of catalyst materials. Preferably, heat treatment is performed at a temperature of, for example, 400 to 700° C. for 2 to 4 hours, but specific heat treatment conditions vary depending on catalyst components and heating temperature.

In the present invention, not only the catalytic metal is chelated with the polycyclic polymer obtained by electrochemically polymerizing heteromonocyclic compounds, but also the low-molecular-weight heterocyclic compound is used as an auxiliary ligand to chelate the catalytic metal, which effectively increases The chelation possibility of the catalyst is improved, and the density of the polycyclic ligand molecules that are supported as active substances is increased.

In the present invention, the term "ancillary ligand" refers to a low-molecular-weight compound that has the function of more completely realizing the catalytic metal binding by helping the "polycyclic molecule derived from a heteromonocyclic compound" to chelate the catalytic metal. Chelation. Preferable examples of such auxiliary ligands include low-molecular-weight heterocyclic compounds. The use of auxiliary ligands can enhance the catalytic activity of catalyst materials. For example, in order to promote chelation of the catalytic metal, it is preferable to chelate a nitrogen-containing low molecular weight compound (which is a low molecular weight heterocyclic compound) as an auxiliary ligand with the catalytic metal. As the nitrogen-containing low-molecular-weight compound, any of various compounds can be used. As the low-molecular-weight heterocyclic compound, any of various compounds can be used. Among low-molecular-weight heterocyclic compounds, pyridine, which has one nitrogen atom as a heteroatom, and phenanthroline, which has two nitrogen atoms as a heteroatom, are preferable.

The noble metal used for the catalyst material prepared in the present invention is not limited to any specific noble metal, and any metal known for use in catalyst materials, particularly fuel cell catalysts, may be used. Combinations of noble and transition metals may also be used. Preferable examples of combinations of noble metals and transition metals include the following combinations: one or more noble metals selected from the group consisting of palladium (Pd), iridium (Ir), rhodium (Rh) and platinum (Pt); and one or A plurality of transition metals selected from the group consisting of cobalt (Co), iron (Fe), molybdenum (Mo) and chromium (Cr). Among these combinations, combinations of iridium (Ir) as a noble metal and cobalt (Co) as a transition metal, rhodium (Rh) as a noble metal and cobalt (Co) as a transition metal, and A combination of palladium (Pd) and cobalt (Co) as a transition metal.

In the present invention, when both the noble metal and the transition metal are chelated as the catalyst, the content of the noble metal in the catalyst material is preferably 20 to 60% by weight. If the content of the noble metal is within this range, an increase in catalyst activity can be observed.

In the present invention, preferably, the raw material used for the above-mentioned composite catalyst metal-containing catalyst material is of high purity. If the raw material used for the catalyst material is of high purity, the catalytic activity is remarkably improved. An example of a method of highly purifying the catalyst material is to use palladium acetate as a palladium material and increase the purity of palladium acetate by known physical or chemical methods. Although the reasons for the improvement in catalytic activity due to the purification of the raw materials used for the catalyst material are not fully understood, this improvement may be due to the improvement in the surface composition of N, Co, Pd, etc. forming active sites, especially due to the introduction of The amount of Pd is significantly increased.

In the present invention, preferable examples of the aforementioned conductive material include metals, semiconductors, carbon-based compounds, and conductive polymers.

Preferably, the catalyst material of the present invention comprises a second metal and/or ions thereof as well as the aforementioned catalytic metals. In view of improvement in activity, it is also preferable to incorporate anions into the catalyst material.

There is no limitation on the shape of the catalyst material of the present invention. For example, it may be a granular, fibrous, hollow or horn-like material.

Secondly, the present invention is a catalyst material prepared by the above method, especially a catalyst for a fuel cell.

Thirdly, the present invention is a fuel cell comprising the above catalyst material as a fuel cell catalyst.

The catalyst material of the present invention is a material prepared by supporting a catalytic metal on a polycyclic polymer obtained under specific electrochemical polymerization conditions. The material has excellent catalytic activity, and when used as a fuel cell catalyst, can improve the power generation performance of the fuel cell.

Brief description of the drawings

Fig. 1 is the flowchart of preparing the cobalt+palladium/polypyrrole/carbon-based catalyst material of Example 1.

Figure 2 is a flow diagram for the preparation of the catalyst material of Example 2 using 2-(lH-pyrrol-3-ylpyridine) as the polymerizable ligand.

Fig. 3 is to use carbon nanotube (CNT) and Black Pearls (brand name) as the flow chart of the catalyst material of preparation embodiment 3 as catalyst carrier.

Figure 4 is a flow diagram for the preparation of the catalyst material of Example 4 using multiple electrochemical polymerizations.

Fig. 5 is a flow chart for the preparation of the catalyst material of Example 5 using multiple electrochemical polymerization in conjunction with auxiliary ligands.

Best Mode for Carrying Out the Invention

The catalyst material of the present invention is prepared by coating the surface of a conductive material with a polycyclic polymer obtained by electrochemically polymerizing a heteromonocyclic compound under specific conditions, and chelating a catalytic metal to the polycyclic polymer on the chelation site of the compound.

Examples of conductive materials that can be used as catalyst materials include metals such as platinum, gold, silver, and stainless steel; semiconductors such as silicon; and carbon-based materials such as glassy carbon, carbon black, graphite, and activated carbon. In view of availability, cost, weight, etc., it is preferable to use a carbon-based material, such as glassy carbon, carbon black, graphite, or activated carbon, as the conductive material. In order to ensure a large surface area, the conductive material is preferably granular, fibrous, hollow or horn-like material, but can also be sheet-like or rod-like material.

Among the granular conductive materials, those with an average particle size of 3 to 30 nm are preferable, and those with an average particle size of 3 to 10 nm are more preferable. As for fibrous, hollow or horn-like conductive materials, carbon fibers (fillers), carbon nanotubes or carbon nanohorns are preferred, respectively.

The polycyclic polymer coating the conductive material is derived from a heteromonocyclic compound. Examples of heteromonocyclic compounds usable as raw materials include monocyclic compounds each having pyrrole, vinylpyridine, aniline, or thiophene as a basic skeleton. In particular, pyrrole, dimethylpyrrole, pyrrole-2-carboxyaldehyde, pyrrol-2-ol, vinylpyridine, aniline, aminobenzoic acid or thiophene are used as heteromonocyclic compounds.

Examples of catalytic metals that can be chelated with the chelating sites of polycyclic polymers include: one or more selected from the group consisting of palladium (Pd), iridium (Ir), rhodium (Rh) and platinum (Pt), etc. and one or more transition metals selected from the group consisting of cobalt (Co), iron (Fe), molybdenum (Mo) and chromium (Cr), etc., which are made into a compound compounded with the noble metal.

As for the method of deriving a polycyclic polymer from any one of the aforementioned heteromonocyclic compounds and coating a conductive material with the polycyclic polymer, an electrochemical polymerization method can be used. The electrochemical polymerization method is a method of electrochemically polymerizing a heteromonocyclic compound on a conductive material to produce a polycyclic polymer, so that the conductive material is coated with the polycyclic polymer, and then applying a catalytic metal to the polycyclic polymer. The action takes place on the ring polymer, so that the chelating site of the polycyclic polymer (when the polycyclic polymer is a nitrogen-containing complex compound, the MN ₄ structural site) supports the catalytic metal.

When the conductive material is a commonly used sheet-like or rod-like material, the electrochemical polymerization of the heteromonocyclic compound on the conductive material can be carried out under conventional conditions using a conventional electrochemical polymerization device. However, when the conductive material used is a fine-grained, fibrous, hollow or horn-like material, it is effective to use a fluidized bed electrode electrochemical polymerization device.

In order to cause a catalytic metal-containing solution to act on conductive particles coated with a polycyclic polymer obtained by electrochemical polymerization (hereinafter referred to as "coated particles"), for example, the coated particles are suspended in a catalyst metal-dissolved in a suitable solvent and reflux the suspension by heating under an inert gas atmosphere.

Wherein the example of the chelating compound that catalytic metal is connected with at least two heteromonocyclic compounds in a chelating manner includes: a cobalt-(poly)pyrrole 1:4 chelating compound represented by the following chemical formula (I);

or

A cobalt-(poly)aniline 1:4 chelate compound represented by the following chemical formula (II).

Also included are chelates in which the compound of formula (I) and the compound of formula (II) are partially complexed.

In the present invention, an example of a chelate compound in which a noble metal and a transition metal are linked to at least two heteromonocyclic compounds in a chelate manner is cobalt-(poly)pyrrole 1:4 represented by the following chemical formula (III-1) A complex of a chelate compound and an iridium-(poly)pyrrole 1:4 chelate compound represented by the following chemical formula (III-2).

Another example of a chelate compound in which a noble metal and a transition metal are connected to at least two heteromonocyclic compounds in a chelate manner is a cobalt-(poly)pyrrole 1:4 chelate compound represented by the following chemical formula (IV-1) and A complex of rhodium-(poly)pyrrole 1:4 chelate compound represented by the following chemical formula (IV-2).

As shown in chemical formulas (I), (II), (III-1) and (III-2), (IV-I) and (IV-2), the chelating compound used in the present invention takes the following form: hetero Heteroatoms of monocyclic compounds (nitrogen atoms when the compound is pyrrole and aniline; sulfur atoms when the compound is thiophene) are chelated with catalytic metals, and if any chelated compound is electrochemically polymerized on the conductive material , the surface of the conductive material is coated with polycyclic complex molecules of polycyclic polymers supporting catalytic metals.

The catalyst material in which the compounds of the above formulas (I) and (II) are composited corresponds to a catalyst material, characterized in that it is prepared by coating a conductive material with a polycyclic polymer derived from at least two heteromonocyclic compounds surface; and to chelate catalytic metals to coatings of polycyclic polymers. The chelating compound represented by the above chemical formula (III-1) and (III-2) and the chelating compound represented by the formula (IV-1) and (IV-2) are equivalent to the catalyst material, and it is characterized in that it is prepared as follows: coating the surface of a conductive material with a polycyclic polymer derived from a heteromonocyclic compound; and chelating catalytic metals of noble and transition metals to the coating of the polycyclic polymer.

When the conductive material is a commonly used sheet or rod material, the electrochemical polymerization of any of the above-mentioned chelating compounds on the conductive material can be carried out under conventional conditions using a conventional electrochemical polymerization device. However, when the conductive material used is fine-grained, fibrous, hollow or angular, a fluidized bed electrode electrochemical polymerization device must be used. The electrochemical polymerization method using a fluidized bed electrode electrochemical polymerization device can be carried out in the same manner as above, provided that any solvent capable of dissolving the above-mentioned chelate compound is used. Among these solvents, water-methanol or water-ethanol mixed solutions are suitably used.

An example of a chelate compound obtained by chelating a catalytic metal with a polymerization product of at least two heteromonocyclic compounds is a cobalt-polypyrrole 1:4 chelate compound represented by the following chemical formula (V-1):

Or the cobalt-polyaniline 1: 4 chelate compound represented by following chemical formula (V-2):

An example of a chelate polymer compound in which a mixed catalytic metal of a noble metal and a transition metal is chelated is a cobalt-polypyrrole 1:4 chelate compound represented by the following formula (VI-1) combined with the following formula (VI-2 ) represents the complex of iridium-polypyrrole 1:4 chelate compound:

Or a complex of a cobalt-polypyrrole 1:4 chelate compound represented by the above formula (VI-1) and a rhodium-polypyrrole 1:4 chelate compound represented by the following formula (VI-3).

The chelated states represented by the above chemical formulas (I) to (VI-3) show the state in which 4 nitrogen atoms or sulfur atoms in the heterocycle are chelated with metals. The 4 nitrogen or sulfur atoms in the heterocycles are not always chelated with metals in realistic polycyclic polymers derived from heteromonocyclic compounds due to their molecular combinatorial properties, bent state, or steric hindrance. But even if only 3 or 2 nitrogen atoms or sulfur atoms are chelated with the metal, if a low-molecular-weight heterocyclic compound is added to the reaction system, the added low-molecular-weight heterocyclic compound acts as an auxiliary ligand, and the low-molecular-weight heterocyclic compound Cyclic compounds can additionally chelate metals.

The chelate compound represented by the following chemical formula (VII) shows a state in which one low-molecular-weight heterocyclic compound pyridine and three pyrrole units in polypyrrole are chelated with iridium, thereby four nitrogen atoms are chelated with iridium atoms.

Compared with the electrode material whose surface is modified by a macrocyclic compound (such as porphyrin), the catalyst material of the present invention obtained as described above, that is, has a polycyclic complex (consisting of a polycyclic polymer, the catalytic metal and the polycyclic Cyclic polymer chelate) coated catalyst material has excellent catalytic activity. And the catalyst material can be used as a catalyst instead of platinum (Pt) or its alloys, for example, as an electrode catalyst for various types of fuel cell cathodes.

Electrode catalyst materials for fuel cell cathodes (oxygen or air electrodes) need to catalyze the oxygen reduction reaction shown below in order to accelerate the reaction. Specifically, when oxygen (O ₂ ), protons (H ⁺ ) and electrons (e ^- ) are supplied, an oxygen reduction reaction, such as the 4-electron reduction of oxygen represented by the following reaction formula (1), or the following reaction formula The 2+2 electron reduction of oxygen represented by (2) and (3) is accelerated by the catalytic action of the catalyst material at an effectively high potential.

<4-electron reduction of oxygen>

<2+2 Electron Reduction of Oxygen>

In the present invention, as described below, the oxygen reduction peak potential obtained by cyclic voltammetry (CV) and rotating disk electrode (RDE) measurement is 0.54 V relative to SCE, and the number of electrons involved in the reaction is close to 4. This performance is comparable to that of platinum or its alloys currently used as electrode catalyst material for fuel cell cathodes (oxygen or air electrodes). This indicates that the catalyst material of the present invention can be used as an electrode catalyst material for fuel cell cathodes (oxygen or air electrodes).

The catalyst material of the present invention obtained as above preferably contains a second metal and/or ions thereof as other metal elements. Examples of second metals and/or ions thereof include: nickel, titanium, vanadium, chromium, manganese, iron, copper, zinc, zirconium, niobium, molybdenum, ruthenium, rhodium, palladium, silver, cadmium, tungsten, osmium, iridium, Platinum, gold and mercury. Among these metals and/or ions thereof, nickel (Ni) is particularly preferably used. Catalyst materials containing a second metal and/or ions thereof may be prepared by adding the second metal and/or ions thereof upon chelation of the catalytic metal (eg cobalt) with chelation sites formed by the polycyclic molecule. For example, a catalyst material containing a second metal and/or ions thereof can be prepared by refluxing a conductive material coated with a heteromonocyclic compound, cobalt acetate, and nickel acetate in a methanol solution.

If the catalyst material of the present invention contains a second metal and/or its ions, its redox performance is greatly improved. Therefore, the catalyst material containing the second metal and/or ions thereof has catalytic performance sufficient to satisfy the requirements for it when used in a fuel cell or the like, and thus has applicability.

In the preparation of the catalyst material according to the invention, it is preferred to thermally treat the catalyst material obtained by chelating the catalytic metal with the chelation sites formed by the polycyclic polymer derived from the heteromonocyclic compound. And more preferably, the heat treatment is performed in an inert gas.

Specifically, a catalyst material comprising a polycyclic polymer is prepared by electrochemically polymerizing a heteromonocyclic compound to produce a polycyclic polymer as described above, thereby coating the conductive material with the polycyclic compound, and then The catalytic metal is allowed to act on the coating, thereby sequestering the catalytic metal to the coating. In this method, the catalytic material is preferably heat-treated after chelating the catalytic metal.

The heat treatment is carried out, for example, in the following manner: the temperature of the catalyst material is raised from the initial temperature (generally room temperature) to a set temperature, kept at the set temperature for a certain period of time, and then gradually lowered. The treatment temperature used for this heat treatment refers to the temperature at which the catalyst material is kept for a certain period of time. For example, the chamber is evacuated to the desired pressure while maintaining at the initial temperature, heated to a set temperature T (T is about 400 to 700° C.) at a heating rate of 5° C./min, and maintained at the set temperature T for 2 to 4 hours and allowed to cool to room temperature over about 2 hours.

As noted above, thermally treating the catalyst material further enhances the redox performance of the catalyst material. In this way, the heat-treated catalyst material is given catalytic performance sufficient to satisfy requirements for it when used in a fuel cell or the like, and thus has applicability.

The present invention will be described in more detail by examples below, but it should be understood that the present invention is not limited to these examples.

[Example 1: cobalt+palladium/polypyrrole/carbon-based catalyst material]

Prepare cobalt+palladium/polypyrrole/carbon-based catalyst material (hereinafter referred to as "Co+Pd/Ppy/C") according to the process shown in Figure 1

(1) "Electrochemical Polymerization"

In 200 ml of water/methanol mixed solvent containing 0.1M ammonium perchlorate or PTS as supporting electrolyte, dissolve 5.4 ml of pyrrole and 3 g of carbon particles (Ketjen Black). After 30 minutes of argon degassing, electrochemical polymerization was carried out for 45 minutes by the potentiostatic method using a fluidized bed electrode, applying voltages of 1.8, 1.2 and 1.3 V to produce polypyrrole-coated carbon particles.

The amount of pyrrole used was 10 times the amount calculated assuming that polypyrrole was attached to the surface area (800 m ² /g) of Ketjen Black carbon particles without leaving voids between them.

(2) "Metallization"

On the polypyrrole-coated carbon particles obtained by the above (1) electrochemical polymerization, cobalt metal and palladium metal were supported in the following manner. Specifically, 2 g of polypyrrole-coated carbon particles, 4.08 g of cobalt acetate, and 1.84 g of palladium acetate were put into a 200 ml eggplant-shaped flask, and DMF was added thereto. After 30 minutes of argon degassing, the mixture was refluxed for 2 hours. The mixture was then suction filtered to remove the solid content, and the solid content was vacuum dried at 120 °C for 3 hours to produce a carbon coated with an electrochemically polymerized polypyrrole film containing pyrrole-cobalt complex (catalyst particle). grain.

(3) Firing

The carbon particles obtained by the above (2) metallization, coated with an electrochemically polymerized polypyrrole film of pyrrole-cobalt complex (catalyst particle), were heat-treated at 600° C. for 2 hours in an argon atmosphere.

Cyclic voltammetry (CV) and rotating disk electrode (RDE) measurements were performed on the heat-treated catalyst material to measure peak potential and peak current density.

The measurement was performed under the following conditions.

[CV (Cyclic Voltammetry) and RDE]

(rotating disk electrode) measurement:

measuring instrument:

Potentiostat [Nikkou Keisoku, DPGS-1]

Function generator [Nikkou Keisoku, NFG-5]

X-Y recorder [Rikendenshi, D-72DG]

Working electrode:

Edge Planed Pyrolytic Graphite (EPG) Electrodes

Reference electrode:

Saturated Calomel Electrode (SCE)

Electrode:

platinum wire

Supporting electrolyte: 1.0M HClO ₄ aqueous solution

Scan range: 600 to -600mV

Scan rate: 100mV/sec (CV), 10mV/sec (RDE)

Rotation rate: 100, 200, 400, 600, 900rpm (RDE)

Measurement methods:

In the CV measurement for the complex alone, the electrode obtained as follows was used as the working electrode: 20 mg of the complex was dissolved in 10 mL of methanol, and 10 μl of the resulting complex solution was poured over edge-planed pyrolytic graphite (EPG) On the electrode, pour 8 μ l of the mixed solution of Nafion and 2-propanol on the EPG electrode.

20 mg of variously treated carbon-based particles were dispersed in 250 μl of Nafion solution, and 20 μl of the dispersion was poured on the EPD electrode.

The results of Example 1 are shown in Table 1.

[Table 1]

Applied voltage [V, vs. Ag/AgCl] solvent supporting electrolyte Peak potential Ep[V, relative to SCE] Peak current density Ip(mA/cm ² ) illustrate 1.8 water/methanol=4/1 NH ₄ ClO ₄ +0.48 2.00 conventional electrochemical polymerization potential 1.2 water/methanol=4/1 NH ₄ ClO ₄ +0.54 4.71 Polymerization potential within the scope of the invention 1.3 water/methanol=1/1 PTS +0.52 4.29 Polymerization potential within the scope of the invention

The results shown in Table 1 illustrate that in cobalt+palladium/polypyrrole/carbon-based catalyst material (Co+Pd/Ppy/C), tuning the preparation conditions (applied potential, supporting electrolyte and solvent composition) during electrochemical polymerization, High oxygen reduction potential and peak current density can be generated, thus making highly active catalysts.

The detailed mechanism of the enhanced catalyst material is still unclear; however, it is clear that tuning the preparation conditions during the electrochemical polymerization limits the occurrence of side reactions (3,4-position cross-linking polymerization), thus the main reaction (2,5-position polymerization, This is highly electronically conductive) to be performed. This high electronic conductivity may contribute to the enhancement of the catalyst activity, especially the reduction current.

In Table 2, the peak potential Ep (V, with respect to SCE), the peak potential (V, with respect to NHE), and the peak current density Ip (mA/cm ² ).

[Table 2]

Comparing the results of Table 2 when a voltage of 1.8V was applied and when a voltage of 1.2V was applied, the effect of the applied potential can be seen. Specifically, when a voltage of 1.8V was applied, the increase in power generation performance due to heat treatment was more pronounced than when a voltage of 1.2V was applied. Comparing the results of Table 2 when a voltage of 1.2 V was applied and when a voltage of 1.3 V was applied, the effect of the supporting electrolyte used can also be seen. Specifically, when a voltage of 1.2 V was applied and NH ₄ ClO ₄ was used as a supporting electrolyte, the increase in power generation performance due to heat treatment was more pronounced than when a voltage of 1.3 V was applied and PTS was used as a supporting electrolyte.

[Example 2: Preparation of catalyst material using polymerizable ligand 2-(1H-pyrrol-3-ylpyridine)]

According to the scheme shown in Figure 2, the catalyst material was prepared using the polymerizable ligand 2-(1H-pyrrol-3-ylpyridine) (pyPy), in 2-(1H-pyrrol-3-ylpyridine), pyridine (which has Strong tendency to chelate with Co) is linked together with pyrrole (which is polymerizable), giving the catalyst material an increased density of "Co-N4 structure".

(1) "Electrochemical Polymerization"

In 200 mL of DMF solvent containing 0.1 M _LiClO4 as a supporting electrolyte, 1.4 g of 2-(1H-pyrrol-3-ylpyridine) (pyPy) and 1 g of carbon particles (Kctjen Black) were dissolved. After 30 minutes of argon degassing, electrochemical polymerization was carried out by the potentiostatic method using a fluidized bed electrode with an applied voltage of 1.0 for 45 minutes to produce poly(2-(1H-pyrrol-3-ylpyridine))-coated carbon particles .

The amount of 2-(1H-pyrrol-3-ylpyridine) used was 10 times the surface area (800 m ² /g) assuming poly(2-(1H-pyrrol-3-ylpyridine)) was attached to Ketjen Black carbon particles, not in The amount calculated by leaving a gap between them.

(2) "Metallization"

Cobalt metal was supported on the poly(2-(1H-pyrrol-3-ylpyridine))-coated carbon particles obtained by the above (1) electrochemical polymerization in the following manner. Specifically, 2 g of poly(2-(1H-pyrrol-3-ylpyridine))-coated carbon particles and 4.08 g of cobalt acetate were put into a 200 ml eggplant-shaped flask, and DMF or methanol was added thereto. After 30 minutes of argon degassing, the mixture was refluxed for 2 hours. The mixture was then suction filtered to remove the solid content, and the solid content was vacuum dried at 120 °C for 3 hours to produce electrochemically polymerized poly(2-(1H- Pyrrol-3-ylpyridine)) carbon particles.

(3) Firing

Carbon particles obtained by the metallization of (2) above, coated with electrochemically polymerized poly(2-(1H-pyrrole) containing cobalt complexes (catalyst particles), were heat-treated at 600 °C for 2 h -3-ylpyridine)) film.

Cyclic voltammetry (CV) and rotating disk electrode (RDE) measurements were performed on the heat-treated catalyst material to measure peak potential and peak current density.

The results of Example 2 are shown in Table 3.

[table 3]

solvent firing Peak potential Ep[V, relative to SCE] Peak current density Ip(mA/cm ² ) illustrate Methanol does not exist +0.01 1.42 comparative example DMF does not exist +0.05 0.62 comparative example DMF Exist (600℃) +0.20 0.89 Embodiment of the invention

The results in Table 3 demonstrate the preparation of fuel cell cathode catalysts using the polymerizable ligand 2-(1H-pyrrol-3-ylpyridine) (pyPy), in which pyridine (the Has a strong tendency to chelate with Co) and pyrrole (which is polymerizable) are linked together, so that the catalyst material has an increased density of "Co-N4 structure", when preparing this catalyst, adjust the preparation conditions (in The solvent used in the metal chelation process, with or without firing), can generate high oxygen reduction potential and peak current density, thereby making a highly active catalyst.

The detailed mechanism of the enhanced performance of the catalyst material is currently unclear; however, 2-(1H-pyrrol-3-ylpyridine) (pyPy) was used, and in 2-(1H-pyrrol-3-ylpyridine), pyridine (which has Strong tendency to chelate with Co) linked together with pyrrole (which is polymerizable), may make the catalyst material densely loaded with active species.

[Example 3: Investigate the conductive material as carrier]

According to the process shown in Figure 3, carbon nanotubes (CNT) and Black Pearls (brand name) were used as catalyst supports to prepare catalyst materials.

(1) "Electrochemical Polymerization"

In 200 ml of DMF solvent containing 0.1 M PTS as a supporting electrolyte, 0.9 ml of pyrrole and 0.5 g of nanotubes (CNTs) were dissolved. After 30 min of argon degassing, electrochemical polymerization was carried out using a fluidized bed electrode by a potentiostatic method with an applied voltage of 1.3 V for 45 min to produce polypyrrole-coated CNTs.

Likewise, 0.9 ml of pyrrole and 0.5 g of Black Pearls were dissolved in 200 ml of a mixed solvent of water/methanol = 4/1 containing 0.1 M of NH ₄ ClO ₄ as a supporting electrolyte. After 30 minutes of argon degassing, electrochemical polymerization was carried out by the potentiostatic method using a fluidized bed electrode with an applied voltage of 1.8 V for 45 minutes to produce polypyrrole-coated Black Pearls.

(2) "Metallization"

On the polypyrrole-coated CNTs obtained by the above (1) electrochemical polymerization and on the polypyrrole-coated Black Pearls, cobalt metal and palladium metal were supported in the following manner. Specifically, 2 g of polypyrrole-coated carbon particles, 4.08 g of cobalt acetate, and 1.84 g of palladium acetate were put into a 200 ml eggplant-shaped flask, and DMF was added thereto. After 30 minutes of argon degassing, the mixture was refluxed for 2 hours. The mixture was then suction-filtered to remove the solid content, and the solid content was vacuum-dried at 120 °C for 3 hours to produce electrochemically coated cobalt/palladium-electrochemically polymerized polypyrrole membrane complexes (catalyst particles). CNTs and Black Pearls of polymerized polypyrrole membranes.

(3) Firing

The CNTs and BlackPearls obtained by the above (2) metallization were heat-treated at 600°C in an argon atmosphere for 2 hours, and the CNTs and BlackPearls were coated with an electrochemically polymerized polypyrrole film containing a cobalt/palladium complex (catalyst particle).

Cyclic voltammetry (CV) and rotating disk electrode (RDE) measurements were performed on the heat-treated catalyst material to measure peak potential and peak current density.

The results of Example 3 are shown in Table 4. The average particle size of CNTs is 3 to 10 nm.

[Table 4]

carbon carrier Peak potential Ep[V, relative to SCE] Peak current density Ip(mA/cm ² ) illustrate CNT (3-10nm) +0.52 4.00 Embodiment of the invention

The results in Table 4 show that using CNTs as carbon supports, catalyst materials with significantly improved catalytic activity can be prepared. In this preparation, the percentage of noble metal supported on the carbon support was 20% by weight, and the total percentage of metals supported on the carbon support was 20 to 25% by weight.

The detailed mechanism of the performance improvement of the catalyst material is still unclear; but using CNTs with higher conductivity than Ketjen Black as a standard carbon material, it is possible to make the catalyst material densely support the active material.

Table 5 shows the relationship between catalyst materials using Black Pearls 2000 (brand name), Ketjen Black (brand name), Prentex XE-2 (brand name), Vulcan XC-72R (brand name) and acetylene black as carbon supports respectively. Compare.

[table 5]

The results in Table 5 show that the catalyst materials using Black Pearls 2000 (brand name), KetjenBlack (brand name) and Prentex XE-2 (brand name) as carbon supports respectively have good power generation performance.

[Example 4: multiple electrochemical polymerization]

According to the flowchart shown in Figure 4, the catalyst material was prepared by repeating electrochemical polymerization and metallization.

(1) "Electrochemical Polymerization I"

In a mixed solvent of 200 ml of water/methanol = 4/1 containing 0.1 M of NH ₄ ClO ₄ as a supporting electrolyte, 0.9 ml of pyrrole and 0.5 g of Ketjen Black were dissolved. After 30 minutes of argon degassing, electrochemical polymerization was carried out by potentiostatic method using a fluidized bed electrode, applying a voltage of 1.8 V for 45 minutes to produce polypyrrole-coated Ketjen Black.

(2) "Metallization I"

On the polypyrrole-coated Ketjen Black obtained by the above (1) electrochemical polymerization, cobalt metal and palladium metal were supported in the following manner. Specifically, 2 g of polypyrrole-coated carbon particles, 4.08 g of cobalt acetate, and 1.64 g of palladium acetate were put into a 200 ml eggplant-shaped flask, and DMF was added thereto. After 30 minutes of argon degassing, the mixture was refluxed for 2 hours. The mixture was then suction filtered to remove the solid content, and the solid content was vacuum dried at 120 °C for 3 hours to produce KetjenBlack coated with cobalt/palladium-electrochemically polymerized polypyrrole membrane complex (catalyst particle I). .

(3) "Electrochemical Polymerization II"

Similar to electrochemical polymerization I, in a mixed solvent of 200 ml of water/methanol=4/1 containing 0.1M NH ₄ ClO ₄ as supporting electrolyte, dissolve the coated cobalt/palladium-pyrrole complex (catalyst particle I) Ketjen Black and 0.9 ml of pyrrole for electrochemical polymerization of polypyrrole membranes. After 30 minutes of argon degassing, electrochemical polymerization was carried out by potentiostatic method using a fluidized bed electrode, applying a voltage of 1.8 V for 45 minutes, resulting in Ketjen Black which was again coated with polypyrrole.

(4) "Metallization II"

On the polypyrrole-coated Ketjen Black obtained by the above (3) electrochemical polymerization, cobalt metal and palladium metal were loaded again. Specifically, 2 g of polypyrrole-coated carbon particles, 4.08 g of cobalt acetate, and 1.64 g of palladium acetate were put into a 200 ml eggplant-shaped flask, and DMF was added thereto. After 30 minutes of argon degassing, the mixture was refluxed for 2 hours. The mixture was then suction-filtered to remove the solid content, and the solid content was vacuum-dried at 120 °C for 3 hours to produce Ketjen coated with a cobalt/palladium-electrochemically polymerized polypyrrole membrane complex (catalyst particle II). Black.

(5) "Firing"

Ketjen Black obtained by the metallization of (4) above, coated with an electrochemically polymerized polypyrrole film of cobalt/palladium-pyrrole complex (catalyst particle II), was heat-treated at 600° C. for 2 hours in an argon atmosphere. .

Cyclic voltammetry (CV) and rotating disk electrode (RDE) measurements were performed on the heat-treated catalyst material to measure the peak potential.

The results of Example 4 are shown in Table 6.

[Table 6]

Number of electrochemical polymerization and metallization Peak potential Ep[V, relative to SCE] illustrate 1 +0.48 comparative example 2 (multiple electrochemical polymerization) +0.50 Embodiment of the invention

The results in Table 6 show that the steps of (1) electrochemical polymerization of polycyclic polymers (Ppy) on conductive materials (carbon) → (2) metallization of catalytic metals (Co, Pd) were repeated twice, followed by After heat treatment, the catalyst material thus prepared has significantly improved catalytic activity.

The detailed mechanism of the improvement in the performance of the catalyst material is currently unclear; however, it is possible to make the catalyst material densely support the active substance by repeating the steps of supporting the polycyclic complex on carbon particles and chelating the catalytic metal with the complex.

[Example 5: Combination of Multiple Electrochemical Polymerization and Auxiliary Ligands]

According to the flow shown in Figure 5, the catalyst material was prepared by repeating electrochemical polymerization and metallization using auxiliary ligands.

(1) "Electrochemical Polymerization I"

In a mixed solvent of 200 ml of water/methanol = 4/1 containing 0.1 M of NH ₄ ClO ₄ as a supporting electrolyte, 0.9 ml of pyrrole and 0.5 g of Ketjen Black were dissolved. After 30 minutes of argon degassing, electrochemical polymerization was carried out by potentiostatic method using a fluidized bed electrode, applying a voltage of 1.8 V for 45 minutes to produce polypyrrole-coated Ketjen Black.

(2) "Metallization I"

On the polypyrrole-coated Ketjen Black obtained by the above (1) electrochemical polymerization, cobalt metal and palladium metal were supported in the following manner. Specifically, 2 g of polypyrrole-coated carbon particles, 4.08 g of cobalt acetate, and 1.64 g of palladium acetate were put into a 200 ml eggplant-shaped flask, and DMF was added thereto. After 30 minutes of argon degassing, the mixture was refluxed for 2 hours. The mixture was then suction filtered to remove the solid content, and the solid content was vacuum dried at 120 °C for 3 hours to produce KetjenBlack coated with cobalt/palladium-electrochemically polymerized polypyrrole membrane complex (catalyst particle I). .

(3) "Electrochemical Polymerization II"

Similar to electrochemical polymerization I, in a mixed solvent of 200 ml of water/methanol=4/1 containing 0.1M NH ₄ ClO ₄ as supporting electrolyte, dissolve the coated cobalt/palladium-pyrrole complex (catalyst particle I) Ketjen Black and 0.9 ml of pyrrole for the electrochemical polymerization of the polypyrrole membrane. After 30 minutes of argon degassing, electrochemical polymerization was carried out by potentiostatic method using a fluidized bed electrode, applying a voltage of 1.8 V for 45 minutes, resulting in Ketjen Black which was again coated with polypyrrole.

(4) "Metallization I"

On the polypyrrole-coated Ketjen Black obtained by the above (3) electrochemical polymerization, cobalt metal and palladium metal were loaded again. Specifically, 2 g of polypyrrole-coated carbon particles, 4.08 g of cobalt acetate and 1.84 g of palladium acetate were placed in a 200 ml eggplant-shaped flask, 0.139 ml of pyridine as an auxiliary ligand was added, and DMF was added thereto. After 30 minutes of argon degassing, the mixture was refluxed for 2 hours. The mixture was then suction-filtered to remove the solid content, and the solid content was vacuum-dried at 120 °C for 3 hours to produce Ketjen coated with a cobalt/palladium-electrochemically polymerized polypyrrole membrane complex (catalyst particle II). Black.

(5) "Firing"

Ketjen Black obtained by the metallization of (4) above, coated with an electrochemically polymerized polypyrrole film of cobalt/palladium-pyrrole complex (catalyst particle II), was heat-treated at 600° C. for 2 hours in an argon atmosphere. .

Cyclic voltammetry (CV) and rotating disk electrode (RDE) measurements were performed on the heat-treated catalyst material to measure the peak potential.

The results of Example 5 are shown in Table 7.

[Table 7]

Number of electrochemical polymerization and metallization Presence or absence of ancillary ligands Peak potential Ep[V, relative to SCE] Peak current density Ip(mA/cm ² ) illustrate 1 does not exist +0.48 2.00 comparative example 2 (multiple electrochemical polymerization) does not exist +0.50 1.70 Embodiment of the invention 2 (multiple electrochemical polymerization) exist +0.52 2.89 Embodiment of the invention

The results in Table 7 show that the steps of (1) electrochemical polymerization of polycyclic polymers (Ppy) on conductive materials (carbon) → (2) metallization of catalytic metals (Co, Pd) were repeated twice, followed by After heat treatment, the catalyst material thus prepared has significantly improved catalytic activity. In particular, metallization with ancillary ligands can increase the catalytic activity of the catalyst material more significantly than metallization without ancillary ligands.

The detailed mechanism of the improvement in the performance of the catalyst material is currently unclear; however, it is possible to make the catalyst material densely support the active substance by repeating the steps of supporting the polycyclic complex on carbon particles and chelating the catalytic metal with the complex. And the use of ancillary ligands potentially increases the amount of catalytic metal that is chelated.

Industrial applicability

The catalyst material of the present invention is a catalyst material prepared by supporting a catalytic metal on a polycyclic polymer obtained by electrochemical polymerization under specific conditions, wherein the catalyst material has excellent catalytic activity and produces Improved effect of suppressing hydrogen peroxide production when used as a fuel cell catalyst. Therefore, the present invention contributes to the widespread use of fuel cells in practice.

Claims (16)

1. prepare the method for catalystic material, comprising: the electrochemical polymerization step promptly, makes the Heteromonocyclic compound electrochemical polymerization, thereby uses the surface derived from many rings ligand molecule coated with conductive material of described Heteromonocyclic compound; And metallization step, that is, catalytic metal being coordinated on the coating of described many ring ligand molecules, described method is characterised in that the electromotive force that applies is 0.8 to 1.5V in electrochemical polymerization.

2. according to the method for preparing catalystic material of claim 1, it is characterized in that described electrochemical polymerization step carries out in water-methanol or water-ethanol mixed solvent.

3. according to the method for preparing catalystic material of claim 1 or 2, it is characterized in that described electrochemical polymerization step is to use NH ₄ClO ₄Or PTS carries out as supporting electrolyte.

4. according to each the method for preparing catalystic material of claim 1 to 3, it is characterized in that using 2-(1H-pyrroles-3-yl pyridines) as described Heteromonocyclic compound.

5. according to each the method for preparing catalystic material of claim 1 to 4, it is characterized in that described electro-conductive material has 500 to 2000m ²The specific surface area of/g.

6. according to each the method for preparing catalystic material of claim 1 to 5, it is characterized in that described electro-conductive material has 3 to 30nm mean particle size.

7. according to each the method for preparing catalystic material of claim 1 to 6, comprising: the electrochemical polymerization step promptly, makes the Heteromonocyclic compound electrochemical polymerization, thereby uses the surface derived from the polycyclic polymers coated with conductive material of described Heteromonocyclic compound; And metallization step, that is, catalytic metal being coordinated on the coating of described polycyclic polymers to form many ring ligand molecules, described method is characterised in that described electrochemical polymerization step and/or metallization step surpass once.

8. according to each the method for preparing catalystic material of claim 1 to 7, it is characterized in that in the electrochemical polymerization step, make at least two kinds of Heteromonocyclic compound electrochemical polymerizations.

9. according to each the method for preparing catalystic material of claim 1 to 8, it is characterized in that in metallization step, make the coordination simultaneously of precious metal and transition metal.

10. according to each the method for preparing catalystic material of claim 1 to 9, also be included in the heat treatment step that carries out after the metallization step.

11., also comprise the lower molecular weight nitrogen-containing heterocycle compound as assistant ligand and catalytic metal coordinate step according to each the method for preparing catalystic material of claim 1 to 10.

12., it is characterized in that described lower molecular weight nitrogenous compound is pyridine and/or phenanthroline according to the method for preparing catalystic material of claim 1.

13. according to each the method for preparing catalystic material of claim 9 to 12, it is characterized in that described precious metal is to be selected from one or more of the group be made up of palladium (Pd), iridium (Ir), rhodium (Rh) and platinum (Pt), and described transition metal is to be selected from one or more of the group be made up of cobalt (Co), iron (Fe), molybdenum (Mo) and chromium (Cr).

14. catalystic material is by according to each method preparation of claim 1 to 13.

15. be used for the catalyzer of fuel cell, comprise by according to each the catalystic material of method preparation of claim 1 to 13.

16. fuel cell, comprise by according to each the catalystic material of method preparation of claim 1 to 13 as the catalyzer that is used for fuel cell.

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